When must I register for sales tax in a US state I sell into?
When the sales into that state cross its economic threshold, measured over a rolling or calendar twelve month period, or when there is physical presence such as inventory, an employee or an office. The threshold is set separately by each state.
The answer differs between the federal level and the states, see the rows below.
The answer by level
Federal level
Physical presence is no longer required: a state may require a remote seller to collect sales tax where the seller has a substantial connection with the state.
South Dakota v. Wayfair, Inc., 585 U.S. 162 (2018)Threshold
Most states set an economic threshold measured in sales into the state over a twelve month period, and some add a separate transaction count.
Remote seller registration thresholds by stateContract rule
Whether the tax may be added to the agreed price depends on the contract, since a sale of goods is otherwise governed by the commercial code as enacted in the state.
U.C.C. Article 2, as enacted state by state
Source lines
- The Supreme Court removed the physical presence requirement and allowed collection duties based on a substantial connection with the state.
- State thresholds are expressed in sales volume, and some states also count the number of separate transactions.
- Inventory stored in a fulfilment centre in the state is physical presence, independent of the economic threshold.
What it means for the company
The liability is the tax that should have been collected, plus interest and penalties, and it accrues from the day the threshold was crossed, not from registration.
| Level | Requirement | Source |
|---|---|---|
| Federal level | Physical presence is no longer required: a state may require a remote seller to collect sales tax where the seller has a substantial connection with the state. | South Dakota v. Wayfair, Inc., 585 U.S. 162 (2018) |
| Threshold | Most states set an economic threshold measured in sales into the state over a twelve month period, and some add a separate transaction count. | Remote seller registration thresholds by state |
| Contract rule | Whether the tax may be added to the agreed price depends on the contract, since a sale of goods is otherwise governed by the commercial code as enacted in the state. | U.C.C. Article 2, as enacted state by state |
What it means for the individual
A sole proprietor selling online has the same duty as an incorporated seller. The obligation follows the sales, not the entity form.
Source lines
- Uniform Commercial Code Article 2, sales of goodsU.C.C. Article 2, as enacted state by state · read 2026-08-25 · proof 3e5306be24fcebc4
- Supreme Court of the United StatesSouth Dakota v. Wayfair, Inc., 585 U.S. 162 (2018) · read 2026-08-25 · proof 3e5306be24fcebc4Official source
- Streamlined Sales Tax Governing BoardRemote seller registration thresholds by state · read 2026-08-25 · proof 3e5306be24fcebc4Official source
Next step
Track sales by destination state monthly, mark every state approaching its threshold, and register before the first taxable sale after crossing.
This page reports what the sources say, with the identifier and address of the publisher. It is not legal advice and does not decide an individual matter.
Next step
Three ways to put the register to work in your own practice.
Start with your task
Litigation
Find support in a judgment
Search guiding decisions, see what became final and follow changes in the law.
In-house, deals
Map the rules in a transaction
Move from theme to act and on to the article that carries the duty.
Compliance
Assess the risk in a process
Risk scoring per legal area, with the sources behind every score.